fine pitch QFP

The most part I have the most difficulty with is a 16mil QFN. We found that reducing stencil thickness to 4mil, and reducing aperatures for the IC by 20%, and setting local fiducials to the IC helped immensely. We used to get 75% or more bridged out of reflow, I'm down to less than 1%.

We've been using AlphaMetals OM-5000 paste with great results.

This was all done on older machines, too.

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We use a 5 mil for 16mil pitch QFPs, Make sure that the stencil has been polished. Type 3 paste. We have used lead free no-clean, lead no-clean, and water soluble lead pastes for these packages. We set the printer for a slow stroke .7 in/min. with the fastest release speed. I would tell you what it is but our printer just has a percentage (10-100% speed).

We need to wipe the stencil after about 10 prints on average.

If you would like to know what paste we use please E-Mail me offline and I will let you know.

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16 thou pitch parts: Use a 5 thou laser cut electropolished stencil with 0.008"x0.045" apertures and type 3 solder paste.

Bridges Connecting or Partially Connecting Adjacent Leads or Lands * Excessive solder paste * Excessive component placement pressure * Solder paste misplacement * Solder paste integrity * Bent leads * Board vibrations during soldering * Lead plating integrity

What does "dry at QFP pins" mean? Is that "no paste"?

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